1. Field of the Invention
This invention relates to a process for the manufacture of a blend composition of a neutralized sulfonated ethylene propylene terpolymer (EPDM) which includes the steps of sulfonating the EPDM dissolved in a solvent to form an unneutralized sulfonated elastomeric polymer. The solution of the unneutralized sulfonated EPDM is quenched with an aliphatic alcohol. The unneutralized sulfonated elastomeric polymer in solution is then neutralized with a neutralizing agent to form the neutralized sulfonated EPDM in solution. A critically selected non-polar backbone process oil is added under agitation to the solution thereby plasticizing the neutralized sulfonated EPDM with the process oil. The neutralized sulfonated EPDM plasticized with the process oil is then recovered from the solution.
2. Description of the Prior Art
Recently, a new class of thermoelastic sulfonated polymers has been described in a number of U.S. patents. These sulfonated polymers are derived from polymeric materials having olefinic unsaturation, especially elastomeric polymers such as Butyl and EPDM rubbers. U.S. Pat. No. 3,642,728, herein incorporated by reference, clearly teaches a method of selective sulfonation of olefinic unsaturation sites of an elastomeric polymer to form an acid form of a sulfonated elastomeric polymer. The olefinic sites of the elastomeric polymer are sulfonated by means of a complex of a sulfur trioxide donor and a Lewis base. The SO.sub.3 H groups of the sulfonated elastomer can be readily neutralized with a basic material to form an ionically cross-linked elastomer at room temperature having substantially improved physical properties over an unsulfonated elastomer. However, these sulfonated elastomers, unlike their covalently cross-linked unsulfonated counterparts, may be processed like a conventional thermoplastic at elevated temperatures under a shear force in the presence of selected preferential plasticizers which dissipate the ionic associations at the elevated temperatures thereby creating a reprocessable elastomer.
The basic materials used as neutralizing agents are selected from organic amines or basic materials selected from Groups I, II, III, IV, V, VIB, VIIB and VIII and mixtures thereof of the Periodic Table of Elements.
U.S. Pat. No. 3,836,511, herein incorporated by reference, teaches an improved process for the sulfonation of the olefinic sites of the elastomeric polymer, wherein the improved sulfonating agent is selected from acetyl sulfate, propionyl sulfate and butyryl sulfate. The neutralizing agents employed to neutralize the acid form of the sulfonated elastomeric polymers are organic amines.
U.S. Pat. No. 3,870,841, herein incorporated by reference, teaches a method of plasticization of the polymeric backbone of a neutralized sulfonated plastic polymer by means of a polymer chain plasticizer which is a liquid compound having a boiling point of at least about 120.degree. F. The polymer chain plasticizer is selected from a dialkyl phthalate, a process oil or an organic acid ester. Additionally, a domain plasticizer can be incorporated into the composition, wherein the domain plasticizer reversibly disrupts the association of the sulfonate groups at a temperature of forming.
U.S. Pat. No. 3,847,854, herein incorporated by reference, teaches a method of improving the processability of neutralized sulfonated elastomeric polymers by the addition of a preferential plasticizer which has at least one functional constituent which exhibits a bond moment whose absolute value is at least 0.6 Debyes, and must be a liquid at the desired processing temperature of the neutralized sulfonated elastomeric polymer.
These aforementioned patents use the same process for the incorporation of either the domain, or polymer chain plasticizer into the neutralized sulfonated elastomeric polymer. This process includes the fluxing of the crumb of the neutralized sulfonated elastomeric polymer on a hot two roll mill. The plasticizer is then added to the hot flux of the neutralized sulfonated elastomeric polymer and mixing is continued until a homogeneous mixture has been obtained. The plasticized sulfonated elastomeric polymer is removed from the mill and ground or diced into a plurality of discrete particles. The process of the present invention overcomes many of the inherent disadvantages of this previously employed process. For example, a large amount of thermal energy is required to flux the neutralized sulfonated elastomeric polymer on the two roll mill. In the present process, there is no requirement for thermal energy input. In the previously employed batch type process, at least two men were required for a substantial period of time, wherein the neutralized sulfonated elastomeric polymer was twice isolated in particle form--namely, as the crumb and as the ground discrete particle. The continuous type process of the present invention eliminates the need for a double isolation of the neutralized sulfonated elastomeric polymer in the particle form. Furthermore, in the present process there is a substantial reduction in the required manhours for plasticization of the neutralized sulfonated elastomeric polymer.
Additionally, in the present process a more uniform dispersion of the plasticizer into the neutralized sulfonated elastomeric polymer is realized due to the increased mobility of both the process oil and the neutralized sulfonated elastomeric polymer in solution thereby allowing a more complete molecular homogeneity of the backbone chains of the oil and polymer. For example, it is extremely difficult to flux on a mill a neutralized sulfonated elastomeric polymer having a viscosity at 200.degree. C. at 0.74 sec.sup.-1 of about 5.times.10.sup.5 to about 1.times.10.sup.7 poises. In order to flux this polymer an excessive amount of shear and thermal energy is required. This shear tends to mechanically cleave the polymer chains resulting in a reduction in molecular weight and an alteration of molecular weight distribution. Sufficient reduction in molecular weight will have a detrimental effect on the resulting physical properties of the product. Even in the fluxed state, the viscosity of the polymer is extremely high thereby resulting in limited mobility of the polymer chains which results in an inferior dispersion of the process oil into the polymer whereas by the solution process of the present invention, an improved dispersion is realized due to increased mobility of the polymer chains in solution.